Similarity aldehydes

Fc(CO)5] reacts similarly. Aldehydes and ketones can also be obtained from N,N-disubstituted amides, and symmetrical ketones are formed by reaction with CO ... 

In general, a mixed aldol reaction between two similar aldehyde or ketone partners leads to a mixture of four possible products. For example, base treatment of a mixture of acetaldehyde and propanal gives a complex product mixture containing two "symmetrical" aldol products and two "mixed" aldol products. Clearly, such a reaction is of no practical value. 

All the derivatives examined above owe their instability to the presence of the furan ring similar aldehydes, carbinols, chlorides, etc. bearing aliphatic and aromatic substituents are not prone to resinify. An analogous singularity of behaviour is encountered in furan polymers, as underlined at the beginning of this chapter. In a polymer prepared from a furan derivative three different situations must be considered ... 

The ion 133 also reacts with epoxides to form y-hydroxy aldehydes after reduction and hydrolysis,and with aldehydes and ketones (16-41). Similar aldehyde synthesis has also been carried out with thiazoles " and thiazolines (five-... 

Geranyl chloride can be prepared from geraniol by the careful use of triphenylphosphine in carbon tetrachloride. Tris(dimethylamino)phosphine reacts with carbon tetrachloride to form the complex (42) which can be used to form the enol esters (43) from acid anhydrides. Similarly, aldehydes form the alkenes (44), and esters or amides of trichloroacetic acid are converted to glycidic esters. ... 

As part of a strategy of employing monosaccharides as a convenient source of chirality, organometallic additions to protected L-erythrulose derivatives have been carried out. Employing silyl, benzyl, trityl, and acetonide protecting groups, the diastereoselectivities obtained are discussed in terms of chelation to the a-and/or the /3-oxygen, and are compared with results for similar aldehydes. 

Several condensation routes to 2,3 -bipyridinones have been reported. Thus 3-acetylpyridine and nicotinaldehyde were condensed to the a,/ -unsat-urated ketone 45, which reacted in a Michael condensation with l-(car-bamoylmethyl)pyridinium chloride (46) to give 2,4-di(3-pyridyl)-6-pyridone (47). Compound 47 was converted to the alkaloid nicotelline 10 by replacement of the hydroxyl group of 47 by chlorine, followed by reductive dehalogenation. Related condensations have been described, including the synthesis of 4,6-diphenyl-2,3 -bipyridine. Similarly, aldehyde 48 was condensed with cyanoacetamide (49) to afford 2-(3-pyridyl)-5-cyano-6-pyridone (50), the cyano group of which was hydrolyzed and decarbox-ylated to 2,3 -bipyridin-6-one. Several modifications and extensions of... 

The ideal derivative is a solid. A solid can be easily purified by crystallization and easily characterized by its melting point. Thus two similar aldehydes or two similar ketones usually have derivatives that have different melting points. The most frequently formed derivatives for aldehydes and ketones are the 2,4-dinitrophenylhydrazone... 

Yamamoto and Maruoka demonstrated that ATPH can discriminate between structurally similar aldehydes, thereby facilitating selective functionalization of the less-hindered aldehyde carbonyl [163]. Treatment of an equimolar mixture of valeralde-hyde (149) and cyclohexanecarbaldehyde (150) with ATPH (1.1 equiv.) in CH2CI2 at -78 °C, then addition of Danishefsky s diene gave hetero-Diels-Alder adduct 151 and 152 in the ratio > 99 1. It is worthy of note that the complexed aldehyde could react with the diene only. The reaction gave relatively low chemoselectivity with other types of Lewis acid (ratio of 1517152 6.2 1 with (Pr 0)2Ti2Cl2 5 1 with McsAl 3.7 1 with MAD 2 1 with TiCU 1.3 1 with BF3-OEt2). This emphasizes that the cavity of ATPH plays an important role in differentiating between the reactivities of the two different aldehydes. In a similar manner, the aldol reaction of a mixture of 149 and 150 was effected with ATPH to furnish 4-hydroxy-2-octanone (153) without formation of 154 (Sch. 122). 

The number of chiral diazaaluminolidine catalysts has been extended by Dymock, Kocienski and Pons, who introduced the more convenient to handle trimethylsilyl-ketene [31]. The catalysts in this study were prepared from slightly different sulfonamides but asymmetric induction was comparable with that obtained with the ketene and similar aldehydes. With trimethylsilylketene, two diastereomers are possible and in all examples studied the cis isomer 126 was the predominate product. TTie reactions in Table 7 were performed with 30 mol % catalyst—with 20 mol % catalyst the reaction is incomplete. A more active catalyst can be prepared from the bis-trifluoro-methylsulfonyl derivative of 128, but asymmetric induction was low. It was reported that ortho substituents on the aryl sulfonamide were necessary for higher induction but data were provided only for the aryl sulfonamide substituents summarized in Table 7. Both symmetrical and unsymmetrical diazaaluminolidines were examined as catalysts in an attempt to optimize asymmetric induction but significant differences were not found. The catalyst prepared from the symmetric bis-sulfonamide 128 with Ar = 2,4,6-tri-/yo-propylphenyl did not give any reaction even at 100 mol %. 

Similarly, aldehyde o-aminophenylhydrazones, available by reduction of the nitro precursors, are converted in the absence of oxygen into 2-substituted benzimidazoles. The reaction is acid catalysed and, although complicated experimentally, gives good yields (67 87%), providing a useful alternative when the 2 substituent may be sensitive. When oxygen is not excluded, benzotriazines form instead 102J. In addition, only fair yields of 1-aminobenzimidazoles are obtained by acid-catalyscd cyclization of N-(o-nitroanilino)-substituted aliphatic amines. Benzotriazoles and benzotriazole... 

Similarly, aldehydes and ketones can have the same overall molecular formula but different structures. Each series contains a carbonyl group (C=0) but in each compound they are attached to different groups. The ketone has always got a C-CO-C chain, whereas the aldehyde has a CHO group which is always at the end of the molecule. The first member of the ketone series, propanone, is isomeric with the aldehyde propanal (Figure 6.4.11). 

These reactions involve two different carbonyl partners. If two similar aldehydes or ketones are reacted, a mixture of all four possible products is formed (e.g. reaction of A and B gives AA, AB, BA and BB). This is because both carbonyl partners can act as nucleophiles and electrophiles. 

N-Sulfonyl imines derived from enolizable aldehydes and ketones are, in principle, capable of tautomerization to the corresponding ene sulfonamides. There has been no systematic study of this process, probably due in large part to the fact that only relatively few sulfonyl imines of this type have to date been prepared and characterized. Trost and Marrs [17], however, have found that aldehyde 35 on conversion to imine 36 using tellurium reagent 3 led to enamide 37 upon workup (Scheme 9). Similarly, aldehyde 38 was converted to imine 39 which tautomerized to 40 upon isolation. 

The photoreduction efficiency of carbonyl compounds such as 9,10-anthraquinone, 1,4-anthraquinone, 6,13-pentacenequinone, and 2-phenyl-9.10-anthraquinone, in the presence of anthracene, pyrene, naphthalene, biphenyl, 1,4-benzoquinone, and 1,4-naphthoqulnone has been shown to depend on the relative positions and nature of the electronic levels of the substrate and acceptor. Photoreduction of aromatic ketones to alcohols or pinacols can be catalysed by CdS powders using triethylamine as sacrificial donor in MeCN, and morphology is reported by the same authors to affect the two-electron transfer photoreductions of aromatic ketones on CdS induced by visible llghti under analogous conditions olefins behave similarly. Aldehydes of the type RCHO (R -jB -tolyl, g-anlsyl, hexyl) have been photoreduced to the corresp>onding... 

The alkylidene-1,3-dicarbonyl moiety is also a highly reactive enophile. Thus, the Knoevenagel adduct (223) obtained from aldehyde (222) and dimethyl malonate in the presence of piperidinium acetate, cy-clizes by treatment with Lewis acids such as FeCb on AI2O3 exclusively to the rranr-substituted cyclohexane (224 trans.cis > 99.5 0.5 Scheme 44).7 °3 The sesquiterpene veticadinol (225) has been synthesized in enantiomerically pure form by this method.Contrary to the expectation, rranr-sub-stituted cyclopentanes can also be obtained with excellent induced and noninduced dia-stereoselectivities. Similarly, aldehydes containing an allylsilane moiety can be used for a highly stereoselective formation of rran.r-l,2-disubstituted cyclopentanes and cyclohexanes by a Knoevenagel... 

The condensation of rhodanine (42) with aldehydes is an important reaction closely related to the Er-lenmeyer azalactone synthesis (equation 22) the resulting condensation products are particularly useful intermediates for the preparation of various functionalized arylacetic acids and derivatives via standard manipulations of the nitrile (43), which is available as illustrated in Scheme 11. Similarly, aldehydes... 

Similarly, aldehydes that form hydrates easily or that are only available as aqueous solutions can be used directly (15). 

Similar aldehydes 143a-b, 143e were also applied by the Cdrdova group, this time in combination with Boc-protected imines 23a, 23c-d (Scheme 5.56). Again, L-proline 1 was successfully utilized to yield the allylic Boc-protected amines 146 in reasonable yield and E/Z selectivity, but excellent enantioselectivity (all >99% ee) [85],... 

Like fluorene, the three methylene moieties in sumanene can undergo alkylation or aldol condensation (Scheme 38). In the presence of a mixture of aqueous NaOH and Bu4NBr, the reaction of 2 with allyl bromide or 4-methoxybenzyl chloride gave the corresponding hexa-alkylated sumanenes 118 [137]. Similarly, aldehydes yielded 119 in two regioisomeric forms [138]. 

Hydroperoxides from lipoxygenase isoenzymes in peas, potatoes and beans produce similar aldehyde mixtures from linoleic and linolenic acids. Peanut lipoxygenase forms pentane and hexanal. Under anaerobic conditions,... 

The Benzoin Condensation. Treatment of benzenecarboxaldehyde (benzalde-hyde, CeHsCHO) and similar aldehydes with sodium cyanide (Na " CN") in ethanol (ethyl alcohol, CH3CH2OH) as solvent at reflux for brief periods results in the formation of a dimer, 2-hydroxy-l,2-diphenylethanone (benzoin) (Equation 9.49). A mechanism has been proposed (Scheme 9.60) that accounts for the following observations ... 

AUylic alcohols can also be accessed from the reductive coupling of allenes and aldehydes. As with the similar aldehyde-alkyne system, trialkylsilanes can be... 

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